G. Grindhammer

Radiative decays of the Jψ and evidence for a new heavy resonance

Abstract The three photon final state produced in e+e− collisions has been measured at the mass of the J ψ resonance using the nonmagnetic part of the double arm spectrometer DASP. The decays J ψ → ηγ, ηγ and πoγ were observed and their branching ratios are given. A four standard deviation signal was observed in the γγ mass spectrum at a mass of (2.83 ± 0.03) GeV. An upper limit is given for the direct decay J ψ → 3γ .

Measurements of

Abstract The cross sections for e+e− → e+(μ+ + non showering track + any photons have been measured for cm energies between 3.1 GeV and 5.2 GeV. We observe τ-pair production below the thresholdfor charm production and determine the τ mass to be 1.807 ± 0.020 GeV from a fit to the energy dependence of the cross section. The ration of the leptonic branching ratios Bμ/Be = 0.92 ± 0.32 is consistent with eμ-universality. The following branching ratios are determined for a V-A coupling: B(τ → ν τ e ν ) = B(τ → ν τ μ ν ) = 0.182 + 0.028 . B(τ → ντ + charged hadron + any photons) = 0.29 ± 0.11, B(τ → ντ + three or more charged hadrons + any photons) = 0.35 ± 0.11.

\tau

Abstract Single electrons produced with hadrons in e + e − collisions at cms energies of 4.0 to 4.2 GeV have been observed at DORIS using the double arm spectrometer DASP. The measured electron spectrum peaks at low momentum and the associated hadron multiplicity is high. These experimental results are consistent with the electromagnetic production and weak decay of a hadron with a new quantum number that is conserved by the strong and electromagnetic interaction. The electron yield at 3.7 GeV (the ψ′ resonance) and at lower energies was found to be consistent with the estimated background, indicating that the production threshold lies between 3.7 and 4.0 GeV.

decay modes and a precise determination of the mass

Abstract Charged hadron production via e + e − → h ± X where h ± = π ± , K ± , p has been measured for s values between 13 and 25 GeV2. Inclusive cross sections and the evidence for scaling are presented.

Evidence for Weakly Decaying New Hadrons in e+ e- Collisions Above 4-GeV CMS

Abstract Inclusive η production by e + e − annihilation for cm energies between 4 and 5.2 GeV was studied. A strong η signal was observed at 4.4 GeV, produced predominantly in conjunction with a low energy photon suggestive of F F ∗ or F ∗ F ∗ production. From events containing a π ± , and η, and a low energy photon the F and F ∗ masses were found to be 2.03 ± 0.06 and 2.14 ± 0.06 GeV, respectively.

Inclusive hadron production by e+e− annihilation for s between 13 and 25 GeV2

Abstract The multiplicity distribution of inclusive electron events above 4 GeV cm energy shows two distinct classes of events: two prong no photon and high multiplicity events. If the high multiplicity events are attributed to the semi-leptonic decay of charmed particles the two prong no photon events must come from the weak decay of a different type of particle. The charged K to π ratio was measured for these events. The average number of charged kaons is 0.07 ± 0.06 per two prong event and 0.90 ± 0.18 per multiprong event. Thus the weak current responsible for the low multiplicity events has a small coupling to strange particles.

Evidence for the F meson

Abstract The semileptonic and leptonic decay modes of charmed hadrons produced in e + e − collisions above 4 GeV in the cm have been investigated by selecting events with a single electron plus at least two charged tracks. The electron momentum spectrum peaks near 0.5 GeV/ c with few events above 0.7 GeV/ c . The spectrum excludes large rates for the decays D → e v e and D → e v e π , but is compatible with D → e v e K ∗ (892) , D → e v e K or a mixture of both. The semileptonic branching ratio is obtained both by comparing the inclusive electron cross section with the total cross section attributable to charm, and by studying the fraction of events containing a second electron. The semileptonic charm branching ratios obtained are 0.11 ± 0.03 and 0.16 ± 0.06 respectively. A single event with three electrons and hadrons is found, consistent with the estimated background. The 90% confidence upper limit for σ (e + e − → 3e + hadrons) is 0.1 nb.

On the origin of inclusive electron events in e+e− annihilation between 3.6 and 5.2 GeV

Abstract The four cross section components σU, σL, σP and σI were separated in the reaction γV+ p → π+ + n at an electron four momentum transfer of Q2 = 0.70 GeV2 and an invariant hadronic mass of 2.19 GeV in the range of t between tmin and −0.28 GeV2. The longitudinal cross section σL dominates at small |t| and decreases rapidly with increasing |t|. The data are in rough agreement with the prediction of a generalized Born term model. The resulting value for the pion electromagnetic form factor is Fπ = 0.42 ± 0.015.

On the semileptonic decay of charmed hadrons

Abstract Momentum spectra and particle ratios are presented for charged pions, kaons and nucleons emitted in the decays of J ψ and ψ.

Separation of σL and σU in π+-electroproduction above the resonance region

Abstract Branching ratios have been determined for the decays of J ψ and ψ ′ into π+π−, K+K−, p p , π±ϱ∓ and K ± K ∗ (892) ∓ . Results on a search for other two body decays of J ψ and ψ′ are given. Also presented are values for the π and K from factors at s = 3.1 and 3.7 GeV .